Inner-cooled generators with singledirection ventilation



A rifi 26, 1955 R. A. BAUDRY El AL INNER-COOLED GENERATORS WITH SINGLE-DIRECTION VENTILATION 5 Sheds-Sheet 1 Filed Nov. 27, 1953 INVENTORS 'Rene' A. Boudry 8 Paul R. HeHer. BY

ATTORNEY April 26, 1955 R. A. BAUDRY EIAL 2,707,243

INNER-COOLED GENERATORS WITH SINGLE-DIRECTION VENTILATION Filed Nov. 2'7, 1955 3 Sheets-Sheet 2 Fig.7.

April 26, 1955 R. A. BAUDRY ErAL 2,707,243

INNER-COOLED GENERATORS WITH SINGLE-DIRECTION VENTILATION Filed Nov. 27, 1953 3 Sheets-Sheet 3 1 8min. ,2 u: IL! an United States Patent INNER-COOLED GENERATORS WITH SINGLE- DIRECTION VENTILATION Reu A. liaudry, Pittsburgh, and Paul R. Heller, Irwin, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 27, 1953, Serial No. 394,602 19 Claims. (Cl. 310-57) Our invention relates to inner-cooled hydrogen-cooled turbine-generators, or other dynamoelectric machines, in which the heat generated in the stator and rotor windings is directly withdrawn from the Winding conductors, through inner-cooling ducts which are disposed in good thermal relation to the winding-conductors.

Heretofore, such inner-cooled machines have been designed with the same kind of stator-core cooling which has been used for several decades in turbine generators, that is, since long before the introduction of inner-cool mg. The conventional method of cooling the statorcores of machines having such large length-to-diameter ratios as are prevalent in turbine-generators, has been to provide the stator-core with a large number of radial ventilating-spaces, which are disposed between small bunches of stator-core laminations, and these radial ventilating-spaces have been surrounded with a plurality of peripheral annular ventilating-zones, which have been alternately intake-zones and outlet-zones. The cooling-gas, which was at first air, but which has been hydrogen since along about 1930, was introduced into the radial ventilating-passages in a zigzag path, which forced the gas first radially inwardly, to the air gap, then radially outwardly in the next group of core-passages to the adjacent outlet-zone surrounding the statorcore, then to the next adjacent inlet-zone surrounding the stator-core, and radially inwardly through those statorcore passages to the air gap, and so on. This used the air gap, so far as the stator-core ventilation was con cerned, only as a means for transferring the coolant from one group of radial inlet-passages to the next adjacent group of radial outlet-passages of the stator-core. The arrangement also commingled the hot gas, which was discharged from the rotor-member into the air gap, with the stator-core cooling-gas, thus considerably increasing the hottest-point temperature of the stator core.

Our experience with inner-cooled turbine-generators has convinced us that the above-described old or conventional stator-core cooling-method is not at all desirable in these machines. The inner-cooling ducts of the stator and rotor windings successfully dissipate all of the copper losses or conductor-heat, into the coolant which flows through these inner-cooling ducts. Consequently, the heat which is to be removed from the stator and rotor cores is only the relatively small amount of heat which is produced by hysteresis and eddy currents within these structures. The rotor-core heat is adequately withdrawn by the coolant which inner-cools the rotor-windings. This leaves, therefore, only the statorcore heat-losses, due to hysteresis and eddy currents, which can be withdrawn by relatively small quantities of coolant.

Considerations such as the foregoing have led us to believe, and tests have verified our predictions, that the total amount of gas, which is required for generators of the inner-cooled type, is substantially smaller than for the conventional type of generator without inner-cooling. In one case, the total volume of cooling-gas which is required by a generator having inner-cooling was less than one half of that which was required for a generator of the same rating, but without inner-cooling.

According to our present invention, it is possible, therefore, to make the air gap of our inner-cooled generator sufficiently large to serve as a hot-gas collecting-chamber and as an axial duct for a substantial portion of the ventilating-gas of the machine. In one form of embodiment, all of the gas which is used for cooling the stator-core passes radially inwardly through the radial core-ventilating passages, and discharges, as hot gas, into the air gap; and substantially all of the rotor-cooling gas, for cooling both the innercooled rotor-windings and the rotor-core, also discharges into the air gap, which thus acts as a hot-gas collecting chamber. The gas is then drawn from one end of the air gap by a special multistage axial blower, and is thence blown through the coolers; and from the coolers, the cooled gas is led into the inner-cooling ducts of the stator and rotor windings, and into the core-cooling passages of the stator core. This arrangement results in the simplest and most efficient utilization of the machine-space, it provides a more efficient blower-system which is capable of producing higher compression-ratios and of supplying lowertemperature gas to the windings, and it permits a frameconstruction which is more suited to operation with the higher gas-pressures which are now preferred in innercooled turbine-generators.

Several different illustrative forms of embodiment of our invention are shown in the accompanying drawing.

Figure l is a side-elevational view, the top half being in longitudinal section, showing a hydrogen-cooled turbine-generator embodying our invention in a form in which we use only a single pair of vertical coolers, disposed at only one end of the machine, and suitable for all except perhaps the very highest ratings of future machines which are larger than any machines thus far sold;

Figs. 2, 3, 4 and 5 are successive transverse sections on the section-planes indicated, in Fig. l, by the lines lI-ll, Ill-Ill, IV-IV and VV, respectively;

Fig. 6 is a partial horizontal sectional view, on the section-plane indicated at VIVI in Fig. 1;

Figs. 7 and 8 are respectively vertical and horizontal longitudinal sections of an alternative machine-design in which the vertical coolers must be used at both ends of the machine, in order to meet the required ratings;

Figs. 9 and 10 are respectively vertical and horizontal longitudinal sections of a generator using a series-blower system, as distinguished from the parallel-blower system which is shown in Figs. 7 and 8;

Figs. 12 and 14 are respectively vertical and horizontal longitudinal sectional views of a machine in which the stator-core is cooled by axially disposed cooling-openings, instead of radially disposed cooling-passages, and in which a dilferent disposition or arrangement of the coolers is provided; and

Figs. 11 and 13 are transverse sectional views on the sections-planes indicated at XI-XI, XIII-XIII in Figs. 12 and 14.

Fig. 1 shows a turbine generator, which is illustrative of a dynamoelectric machine having a stator member 15 and a rotor member 16, separated by an air gap 17.

The stator member 15 includes a substantially gas-tight machine-enclosing housing, which comprises an outer cylindrical frame-shell or core-surrounding housing-portion 18, and two brackets 19 and 20, enclosing the respective ends of the outer frame-shell. The housing is filled with a gaseous filling, which is preferably hydrogen, at a gaspressure which is adapted, at times, to be at least as high as 30 pounds per square inch, gauge, which may be regarded as a minimum pressure, as somewhat higher gaspressures are contemplated. While hydrogen is preferred, it is possible to use other gases having a molecular weight lower than nitrogen, the low molecular weight being desirable in order to keep down the windage-losses resulting from the rotation of the motor member 16 within the gas.

The stator member 15 also comprises a cylindrical stator-core 21, having a plurality of winding-receiving stator-slots 22. The stator member also comprises an inner-cooled stator winding 23 having coil-sides lying within the winding-receiving slots 22, and coil-ends lying beyond the respective ends of the stator-core 21. This stator winding 23 is an inner-cooled winding, having cooling-ducts 24 which are in good thermal relation to the stator-conductors, for substantially directly cooling said stator-conductors. The stator-winding cooling-ducts 24 have inlet-openings 2411 at one end of the winding, and outlet openings 24b at the other end.

A recirculating stator-winding cooling-system is necessarily provided, for recirculating a stator-winding coolingfluid in said inner-cooling stator-winding ducts 24, said recirculating cooling-system including a means for cooling the stator-winding cooling-fluid. Although it is not necessary to use the gas which fills the machine-housing as the stator-winding cooling-fluid, we prefer to do so, in which case, the duct-inlets 24a are open to an endspace 24' within the machine, at one end of the machine, while the duct'outlets 24b are open to another end-space 34" within the machine at the other end of the machine, thus cooling the stator winding 23 with the gas which is enclosed within the machine-housing, said gas being cooled by the subsequently described coolers. The stator winding 23 is usualy a polyphase winding, and in the large machine-sizes to which our present invention is particularly applicable, the stator Winding 23 is provided with ground insulation 25 which is good for 10,000 volts, or higher.

The stator-core 21 is also provided with a plurality of core-ventilating stator-ducts, which may be either radially disposed ducts or spaces 26, as shown in Figs. 1 to 10, or axially disposed ducts or holes as shown in Figs. 11 to 14.

The rotor member 16 has a cylindrical rotor core 28, which has a plurality of axially extending winding-receiving slots 29, and an inner-cooled rotor winding having cooling-ducts 31 in good thermal relation to the rotor-conductors for substantially directly cooling said rotor-conductors. Preferably, or in practically every case in which our invention would be used, the rotorwinding cooling-ducts 31 have inlet-openings or means, 32, at the respective ends of the rotor winding, and outletopenings 33 at a plurality of intermediate discharge-points within the winding-receiving rotor-slots, these dischargepoints being commonly grouped together near the center of the rotor-core, and being connected to the air gap 17 by a plurality of radially extending rotor ducts or holes 34 which discharge the rotor-cooling gas to the rotorperiphery. The rotor windings 30 are insulated for a voltage which is considerably lower than the stator windings 23, so as to require a much thinner rotorinsulation, which is too thin to be shown on the scale to which our drawings are drawn.

The rotor core 28 is carried by a rotor shaft 35, which is supported by a pair of bearing housings 36 near the respective frame-brackets 19 and 20. Associated with the bearing-housings 36, are suitable gland-seal members 37 for maintaining gas-tight joints around the respective shaft-ends. One end of the shaft is connected to a coupling 38, whereby the machine may be connected to a turbine or other prime mover; while the other end of the shaft carries two slip rings 39 for exciting the rotor winding 30, which serves as the field-winding for the machine.

The air gap 17 has a single gap-length of the order of from three and one half to five inches, more or less, so that the air gap is sufiiciently large to act as a hot-gas collecting-chamber and as an axial duct for a substantial portion of the ventilating-gas of the machine, as will be evident from the subsequent explanations.

It is necessary to provide a gas-moving means, for maintaining a circulation of the gas within the machineenclosing housing 1819-20. In the form of embodiment of our invention which is shown in Figs. 1 to 6, this gas-moving means comprises a single evacuating blower 41, carried by the rotor member at one end of the rotor core, and directed so as to evacuate hot gas from that end of the air gap 17, and also from the stator endspace 24" in which the stator-winding duct-outlets 24b discharge. The blower 41 includes a supporting-means of such nature that it provides one or more axially extending under-blower passages 42, extending axially underneath the blower 41. The blower 41 is preferably a multistage blower, which is capable of developing a considerable blower-pressure for rapidly moving the hot gases in an axial direction.

It is necessary to provide a heat-exchanging means, which is disposed within the machine-housing 1819- 20, for cooling the circulated gas. In accordance with our invention, we may use any kind or description or placement of the heat-exchanging means or coolers. We prefer, however, to use the vertically disposed coolers which are described and claimed in a copending application of the applicant Baudry, Serial No. 389,349, filed October 30, 1953, as shown in our Figs. 1 to 10. In the form of our invention shown in Figs. 1 to 6, the heatexchanging means comprises a pair of vertical coolers 44 and 45. These coolers are located axially between the stator-winding duct-outlets 24b and the housing-bracket 20 at that end of the machine, as shown in Fig. 1. The blower 41 is disposed underneath, or within the axial confines of, the stator-winding end-turns which have the duct-outlets 24b, so that the blower 41 discharges the hot gas axially toward the portion of the housing which is occupied by the pair of coolers 44 and 45. The two vertical coolers 44 and 45 are located radially between the bearing housing 36 and the outer frame-shell 18, as shown in Fig. 6, so that the hot gas which is discharged axially from the blower 41 divides into two streams, one stream flowing to the right, through the vertical cooler 44, while the other stream flows to the left, through the vertical cooler 45, as shown in the horizontal sectional view, which is Fig. 6.

Each of the coolers 44 and 45 comprises a plurality of substantially straight, vertical, liquid-cooled, finned pipes, each end of each cooler terminating in a cooler-head 47. The outer frame-shell 18 is provided with cooler-accommodating perforations 48, having pressure-resistant reinforcing means 51, which are secured to the frame-shell around each perforation 48. The top and bottom coolerheads 47 of each cooler 44 and 45 are hermetically but removably secured to their own reinforcing-means 51, so that each cooler can be lifted vertically out of the machine, after disconnecting its two cooler-heads 47. The water-connections, for circulating water or other coolant through the cooler-pipes, are preferably provided at the lower cooler-head 47, as shown in Figs. 2 and 3.

We provide suitable hot-gas guiding means, for guiding the hot gases to and through the blower 41 and the coolers 44 and 45. Thus, the endwinding space 24" into which the stator-winding duct-outlets 24b discharge is confined by an outer cylindrical or arcuate partition 53, a fiat transverse plate or disc 54 which extends vertically between the two coolers 44 and 45 on the sides thereof closest to the stator end-windings, and the shroud 55 of the blower 41. The transverse plate or disc 54 is provided with a central hole 54a which is more or less hermetically joined to the outer periphery of the blowershroud 55.

Surrounding the inner end of the bearing, in the space between the two vertically disposed coolers 44 and 45, there is a stationary funnel-like duct-member 56, the inner end of which comes into near contact with the rotating end of the blower 41, so that there is little gasleakage at this point. This keeps the hot discharge-gases from the blower away from the inner end of the hearing, at the point where the discharged hot gases divide into two streams, flowing to the right and the left to enter the coolers 44 and 45, respectively.

Extending vertically between the two coolers 44 and 45, at their sides closest to the housing-bracket 20, there is a curved transverse plate or disc 57, which bulges or is curved, inwardly, toward the disc 54, and away from the housing-bracket 20. This curved transverse plate or disc 57 has a central hole 57a which is substantially hermetically sealed to the large end of the funnel-like member 56, so as to provide a separation between the hot gas which is flowing to the right and left between the two vertical coolers 44 and 45, and cold gas which flows radially inwardly in the flat end-space 57b between the curved plate 57 and the bracket 20, and then axially inwardly through the funnel-like member 56, into the under-blower passages 42, to ventilate that end of the rotor-windings, as will be subsequently described.

The cold gas, which is delivered from the coolers 44 and 45, is used for the inner-cooling of the rotor winding 30, the inner-cooling of the stator winding 23, and the cooling of the stator-core 21. In the particular construction which is shown in Figs. 1 to 6, these functions are accomplished by a structure in which some of the cold gas is led into both ends of the rotor winding 30, some to the inlets 24a of the stator winding 23, and some to the outer peripheries of the radial cooling-ducts 26 of the stator core. An essential feature of this construction is the provision of an axially extending, peripherally disposed, through duct-means, such as a duct 58 (Fig. 1), to provide an axial communication from one end of the machine to the other. In the form of embodiment shown in Fig. l, the through-duct 58 is illustrated as being in the space between the outer periphery of the stator core and the outer frame-shell 18.

In the construction which is shown in Fig. 1, the stator member is provided, as is well known, with a plurality of axially spaced frame-rings 61 to 64, extending inwardly from the outer cylindrical frame-shell 18 in the axial length which is occupied by the stator core 21. The frame-ring 61 is secured to one end of the cylindrical or arcuate partition 53, which surrounds the hot-gas discharge-end space 24" of the stator-winding ventilation. The space 53a outside of this cylindrical or arcuate partition 53 is filled with cooled gas which is delivered by the two coolers 44 and 45. The through-duct 58 in Fig. 1 extends from this cool-gas space 53a outside of the cylindrical or arcuate partition 53, all the way through the machine, to discharge, beyond the frame-ring 64, in the end-space 24' which feeds said cool gas to the statorwinding duct-inlets 24a, and to the rotor-winding inletopenings 32 at that end of the machine.

As shown in the horizontal sectional view, Fig. 6, the cool-gas space 53a which is outside of the cylindrical or arcuate partition 53 is also in communication with the radial space 57b between the curved transverse plate 57 and the housing-bracket 20; and hence some of the cooled gas is supplied to the rotor-winding inlet-openings 32 at this end of the machine.

At the other end of the machine, the cold-gas end-space 24 is nearly altogether, or substantially, closed off from the end of the air gap 17, at that end of the machine, by means of a stationary cylindrical bafile-member 69 (Fig. 1), which has a small clearance with that end of the rotor member 16, so as to limit, or substantially stop, the escape of cool gas directly from the end-space 24' into that end of the air gap 17, as described in our Patent No. 2,626,365, granted January 20, 1953.

The through-duct 58 is provided with lateral openings 70 for discharging the cooled gas into the annular spaces 70 between the successive frame-rings 61 to 64, these annular spaces 70 being disposed between the outer periphery of the stator-core 21 and the outer cylindrical frame-shell 18. Since the radial stator-core coolingspaces 26 are in communication with these annular framering spaces 70, the cooled gas is thus led radially inwardly, through all of these radial cooling-spaces or ducts 26 of the stator core, thereby cooling the stator core, and discharging the heated core-cooling gas into the air gap 17. A suitable resistance to the flow of this core-cooling gas is provided by a proper restriction of the size of the openings 70 in the through-duct 58, so as to properly control the division of the gas-flow, so that each part receives the quantity of gas which is required to cool the same.

The cool-gas space 53a which is outside of the cylindrical or arcuate partition 53 may contain a fifth framering 71, which is provided with a plurality of openings 72 therethrough, as shown in Fig. 4, so that the entire space outside of this cylindrical or arcuate partition 53 is in effect a single space 53a, all portions of which are in communication with each other.

The operation of the form of embodiment of our invention which is shown in Figs. 1 to 6 may now be summarized. The blower 41 exhausts the hot gases from the air gap 17, and from the stator-winding outlet-end 24" in the space inside of the cylindrical or arcuate partition 53. The blower delivers this hot gas, in two streams, so that it spreads to the right and to the left and flows laterally through the two vertical coolers 44 and 45, respectively.

The gas which is discharged from the coolers 44 and 45 is cold or cooled gas, which appears in the space 53a outside of the cylindrical or arcuate partition 53. A part of this gas flows into the side edges of the flat end-space 57b between the curved transverse plate or disc 57 and the housing-bracket 20, and it flows radially inwardly through this space. As shown in the vertical sectional view, Fig. 1, this gas then flows axially through the funnel-like duct or partition 56, so that it passes through the under-blower passages 42 and enters the rotor-winding inlet-openings 32 at that end of the machine.

The remainder of the coolair in the space 53a outside of the cylindrical or arcuate partition 53 leaves that space through the through-duct 58. A part of this throughduct gas is discharged through the duct-openings 70 into the peripheral annular stator-core ventilating-spaces 70' between the successive frame-rings 61 to 64, thence flowing radially inwardly through all of the stator ventilating-spaces 26, and discharging into the air gap 17 which serves as a hot-gas collecting-chamber.

The portion of the cool gas which flows all the way through the through-duct 58 is discharged into the coolair end-space 24', where most of it divides between the stator-winding duct-inlets 24a and the rotor-winding inletopenings 32 at that end of the machine. A very small portion of the cool gas in this end-space 24' is admitted to that end of the air gap 17, by means of the baffle 69. In some machines, however, this baffie 69 may block substantially all gas-flow into that end of the air gap.

The inner-cooling gas, for the stator-windings 23 in Fig. 1, enters the inlets 24a from the end-space 24', and it passes all the way through the stator-winding coolingducts 24 from that end of the machine to the other end of the machine, where it is discharged, as hot gas, through the outlets 24b, into the space 24" inside of the cylindrical or arcuate partition 53, where it merges with the hot gas which is being delivered from the air gap 17. This merged hot gas is then picked up by the blower 41, and the recirculating process is continued.

The inner-cooling gas, for the rotor winding 30, in the form of our invention which is shown in Fig. l, enters the rotor-winding inlet-openings 32 at both ends of the rotor winding 30. A small portion of this rotor-winding cooling-gas may be bypassed directly into the air gap 17, immediately after having cooled the end-winding portions of the rotor winding 30, as shown by the small openings 73 in Fig. l. The major portion of the rotorwinding cooling-gas flows axially through the rotor-winding inner-cooling ducts 31, from both ends, towards the center of the rotor core 28, at which point the heated gas is discharged to the air gap 17 through the dischargeopenings 33 of the inner-cooling ducts 31 and through the radial rotor-ducts 34.

It will be noted that our invention, as embodied in Figs. 1 to 6, uses a large air gap 17, to receive the bulk of the coolant from the stator-core cooling-vents 24 and from the rotor-winding discharge-ducts 34, discharging this hot gas axially to a high-pressure, multistage axial blower 41 which is located at one end of the rotor member. The high-pressure gas is then blown through suitable coolers, and the cooled high-pressure gas is then distributed to the various inlet-openings for cooling the inner-cooled rotor-windings 30, the inner-cooled statorwindings 23, and the stator-core 21. This arrangement greatly simplifies the amount of battling which is necessary to properly conduct and distribute the coolant. It results in the simplest and most efiicient use of the machine-space. It provides a more efiicient blower-system, Which is capable of recirculating the coolant at higher blower-pressures and higher coolant-velocities, as a result of the use of a single multisiage blower, as distinguished from two smaller blowers, one at each end of the rotor member, thus involving only one velocity-head loss, and more blower-pressure, than the sum of the pressures which would be obtained from two separate blowers.

The use of a single multistage axial blower or compressor 41 is made possible by the reduced volume of gas which needs to be handled in our invention, this reduced volume being made possible by the use of denser gas (or higher gas-pressures), and the use of higher gasvelocities, resulting in a greater blower-efiiciency, which results from handling a reduced volume of gas at higher velocities.

Our use of an exhaust-blower 41, for drawing the hot gas out of the ventilating parts of the machine and passing said hot gas directly through a cooler or coolers before recirculating the same through the ventilating passages of the machine, has an additional advantage, because a high-pressure fan produces an appreciable temperature-rise, as a result of compression, if the gas has a density approaching that of air. In the factory-testing of the machine, it is desirable to first operate the machine in air, for routine electrical and dielectric tests, and for balancing the machine. Our use of an exhausting blower, as distinguished from a blower which blows the gas from the cooler into the ventilating passages of the machine, thus has the advantage of avoiding blowing, into the machine, during these preliminary air-tests at the factory, air which has been heated, by the compressing action of the multistage blower, to a temperature which is too high for the machine-windings. Subsequently, when the air is evacuated or blown out from the machine, and

replaced with hydrogen, our evacuating high-pressure blower avoids the introduction of even the small temperature-rise which is produced by the compression of the hydrogen in the blower, because this compressed hydrogen is passed first through the cooler of coolers, before being passed on into the ventilating passages of the machine.

By avoiding mixing or commingling some of the heated gas with other gas-portions which were not heated, as in previous ventilating-systems which did not use the air gap as a collecting chamber for the hot gas, we achieve, or are able to use, a hotter temperature for the hot gas, which increases the temperature-differential between the gas and the water, in the cooler, thus increasing the efficiency of the cooler for this reason also.

There are many different forms of embodiment in which our invention may be applied.

Figs. 7 and 8 show a form of embodiment of the invention, in a parallel-blower system which is useful where coolers must be used at both ends of the machine, either in order to meet the required ratings, either because of cooler-limitations or ventilation-characteristics, or in order to make two ditferent blower-pressures available, one for the inner-cooled windings 23 and 30, and the other for the stator core 21, as described and claimed in a copending application of Kilgore, Baudry and Heller, Serial No. 394,622, filed November 27, 1953.

In the machine shown in Figs. 7 and 8, the pair of vertical coolers 44, which are located at the machine-end which is bounded by the bracket 21), is duplicated by another pair of vertical coolers 74 at the machine-end which is bounded by the bracket 19. This second pair of coolers, 74, may be of the same description as the first pair, 44, except that the second coolers may sometimes be somewhat smaller. The second pair of coolers, 74, use the same kind of bathing or partition-members as the first pair of coolers, 44, as shown at 54', 55, 56 and 57', these parts corresponding to the correspondingly numbered unprimed parts at the other end of the machine.

In Figs. 7 and 8, the air-gap baffie 69 of Figs. 1 to 6 is omitted, and is replaced by a second exhaust-blower 76, which is disposed to exhaust some of the hot gases out of that end of the air gap 17. This second blower 76 develops a much lower blower-pressure than the firstdescribed multistage blower 41. In the illustrative example in Figs. 7 and 8, this second blower 76 is shown as a single-stage blower. Otherwise, the second blower 76 is of the same description as the first blower 41, and

it is provided with the same underblower passages 42.

In order to segregate the suction-side of the second blower 76 from the high-pressure cool-gas end-space 24 which services the inner-cooled windings 23 and 30, the rotor-member is provided with a cylindrical baffle 77 which is secured to the periphery of the stator core 21 at that end of the machine, and which extends close to the blower-shroud 55 which surrounds the blower 76.

As shown in the horizontal sectional view, Fig. 8, the cool-gas discharge-sides of the second pair of vertical coolers, 74, are partitioned off from the high-pressure cool-gas end-space 24 by transversely disposed vertical barrier-plates 78. As a consequence of the addition of these barrier-plates 78 as shown in Fig. 8, it is necessary to provide a communication-means between the highpressure coolgas end-space 24' and the under-blower passages 42 at that end of the machine, by a means which is shown in the vertical sectional view, Fig. 7, this means including a plurality of ducts 79 between the plates 54 and 57', so that some of the high-pressure cooled gas is diverted or discharged from the end-space 24' which services the stator-winding duct-inlets 24a, and this highpressure cooled gas is delivered through the ducts 79 to the flat end-space 57b between the curved transverse plate or disc 57' and the housing-bracket 19, being thence delivered to the large end of the funnel-like member 56, and thence delivered to the under-blower passages 42 under the blower 76, to service that end of the innercooled rotor-windings 30.

In the large machine which is shown in Figs. 7 and 8, the stator-frame has six frame-rings 81 to 86, instead of the four frame-rings 61 to 64 of Figs. 1 to 6. These six frame-rings 81 to 86 are axially spaced from each other, within the axial length which is occupied by the stator core 21, the frame-rings 81 and 86 being more or less hermetically sealed with respect to the respective ends of the stator core. As in Figs. 1 to 6, these six framerings 81 to 86 are traversed by a through-duct 88, as shown in Fig. 7. This through-duct 88 carries the highpressure cool gas, from the space 53a outside of the cylindrical or arcuate partition 53, to the end-space 24 which surrounds the stator-winding duct-inlets 24a.

However, unlike the through-duct 58 of Fig. 1, the through-duct 88 of Fig. 7 is imperforate along its sidewalls, so that it does not deliver any gas to the annular spaces 70" between successive frame-rings 81 to 86. These annular spaces 70" between successive framerings 81 to 86, as shown in Fig. 8, are in communication with each other, through openings 82 to 85' in the intermediate frame-rings 82 to 85, and the whole group of these annular spaces 70 is placed in communication with the output-sides of the low-pressure coolers 74, by means of ducts 89 (Fig. 8), extending from the barrierpiates 78 to the frame-ring 86.

The operation of the machine which is shown in Figs. 7 and 8 will now be apparent. The hot gas, from the discharge-end space 24" of the stator windings 23, and from the same end of the air gap 17, is compressed to a high blower-pressure by the multistage exhaust-blower 41, and is delivered through the pair of coolers 44 to the high-pressure cool-gas space 53a which is outside of the cylindrical or arcuate partition 53 at that end of the machine. This high-pressure cool-gas space 53a is in communication with the rotor-winding inlet-openings 32 at that end of the machine, through the inwardly curved portion of the transverse plate or disc 57, as shown in Figs. 7 and 8; this air passing radially inwardly between this curved plate 57 and the housing-bracket 20, to the funnel-like member 56.

The high-pressure cool-gas end-space 53a which is fed by the discharge-sides of the coolers 44, is plaeed in communication with the high-pressure cool-gas end-space 24' at the other end of the machine, as shown by the throughduct 88 in Fig. 7. This high-pressure cool-gas endspace 24' encloses the stator-winding duct-inlets 24a, so as to feed gas into these inlets. It is also in communication with the rotor-winding inlet-openings 32 at that end of the machine, through the ducts 79 and the flat endspace 57b between the curved plate 57' and the housingbracket 19. It will be noted that this high-pressure cool gas, for inner-cooling both the stator and rotor windings 23 and 30, is kept separate from the cool gas which ventilates the stator-core 21.

The stator-core ventilation, in Figs. 7 and 8, is obtained from the single-stage exhaust-blower 76, which draws the necessary quantity of hot gas out of that end of the air gap 17, and compresses it to a much lower blower-pressure than is obtained in the multistage blower 41. This compressed hot gas from the single-stage blower 76 is delivered through the second pair of vertical coolers, 74, and the discharge-sides of these coolers are placed in communication, by the ducts 89 in Fig. 8, with the annular spaces 70" between the successive frame-rings 81 to 86, these annular spaces 70" being in communication with the outer peripheries of all of the radial stator-core ventilating-spaces 2.6, which dis charge their hot gases into the air gap, after cooling the stator core 21. In this way, the necessary low pressuredifferential, which is needed to provide the relatively small amount of stator-core cooling, which is necessary, is obtained from a low-pressure blower 76, thus avoiding the expense of first compressing that quantity of gas to the same high pressure-differential which is needed for the inner-cooling of the windings, and then throttling it down to the pressure-differential which is needed by the stator-core cooling-spaces 26.

A series-blower system, such as is shown in Figs. 9 and 10, is suitable for those turbine-generators in which a gas-d1scharge from only one end of the air gap is practicable, and where the savings in the blower-power requirements will justify the slight additional complication wltilrch is required by using two blowers in series with each ot er.

In Figs. 9 and 10, we show two blowers 91 and 91', one at each end of the rotor-core. Both of the blowers 91 and 91', in Figs. 9 and 10, are shown as single-stage blowers, because, as will subsequently appear, the two blowers are connected in series with each other, for producing the pressure-differential which is needed for the inner-cooling of the stator and rotor windings 23 and 30, whereas the stator-core cooling is obtained from the pressure-differential which is created by the blower 91 alone, as will subsequently appear.

Of these blowers 91 and 91', in Figs. 9 and 10, the blower 91 is an exhaust-blower, for evacuating gas out of that end of the air gap and also from the chamber 24" which receives the gas from the stator-winding ductoutlets 24b, as was the case with the multistage blower 41 in Figs. 1 to 8. This blower 91 is provided with the previously described under-blower passages 42, and it delivers its hot gas to a single pair of vertical coolers 44 and 45, with the same bathe or partition-arrangement which has already been described for the end of the machine which is bounded by the frame-bracket in Figs. 1 to 8 The stator member in Figs. 9 and 10 has four framerings 92 to 95, corresponding to the six frame-rings 81 to 86 of Figs. 7 and 8. Each of these frame-rings is perforated, as shown at 92' to 95', thus putting the cool-gas zone 53a, which surrounds the cylindrical or arcuate partition 53, into communication with the sim ilar zone 96, which surrounds a cylindrical or arcuate partition 97 at the other end of the machine, that is, at the end which is bounded by the housing-bracket 19. The frame-ring perforations 92', 93 and 94 also put the first cool-gas zone 53a into communication with the annular frame-ring spaces 70 which are in communication with the outer peripheral ends of all of the radial ventilating-spaces 26 of the stator-core 21.

In Figs. 9 and 10, the second blower 91 blows the gas axially inwardly toward the stator and rotor cores 21 and 28. This blower 91 receives gas, on its intake side, through a passageway 98 which is in communication with the outer cool-gas zone 96 which surrounds the cylindrical or arcuate partition 97. The blower 91 adds its blower-pressure to that of the first mentioned blower 91, thus creating a combined pressure-differential which blows the cooling gas into a high-pressure inner cool-gas zone 99, which is in communication with the stator-winding duct-inlets 24a and with the rotorwinding inlet-openings 32 at that end of the machine. The air gap 17, at this end of the machine, that is, adjacent to the inner cool-gas zone 99, is blocked, or nearly blocked, by a suitable annular or cylindrical baffle 100, such as is described and claimed in our Patent No. 2,626,365.

As shown in Fig. 9, the cylindrical or arcuate partition 97, which constitutes the outer boundary of the high-pressure cool-gas zone 99, is provided with an out let-opening 101, which is connected, through a throughduct 102, to the curved transverse plate or disc 57, thus transmitting the high-pressure cooling-gas to the flat endspace 57b between this plate or disc 57 and the framebracket 20, at the same end of the machine at which the coolers 44 and 45 are located, thus delivering the gas, through the funnel-like member 56 and the under-blower passages 42, to the rotor-winding inlet-openings 32 at that end of the machine. The through-duct 102 is illustrated in Fig. 9 as being disposed in the annular space between the outer periphery of the stator core 21 and the outer cylindrical frame-shell 18, and it passes through suitable holes, which are provided especially for said duct in the frame-rings 92 to 95, as shown in Fig. 9.

In the operation of the form of embodiment of our invention which is shown in Figs. 9 and 10, it will be obvious that the first blower 91 receives all of the hot gas, and delivers it through the two vertical coolers 44 and 45 to the first cool-gas zone 53a at a pressure which is suitable for forcing the necessary amount of cooling-gas through the radial ventilating-ducts 26 of the stator core 21, these stator-ducts discharging their heated gases into the air gap 17. The rest of the partially pressurized cooling-gas, which is not diverted through the stator-core ducts 26, passes on, through the frame-ring perforation 95, to the outer zone 96, from which this gas enters the second blower 41, which adds its blower-pressure to that of the first blower 41, and thus creates a high-pressure cooling-gas, which is used to enter the stator-winding inner-cooling ducts 24 at that end of the machine, and to enter the rotor-winding inlet-openings 32 at both ends of the machine. The statorwinding ducts 24 discharge their heated gas into the hotgas zone 24" which is in communication with the inlet side of the first blower 41. The heated rotor-winding cooling-gas is discharged through the discharge-openings 10 34 of the rotor-core, into the air gap 17, from which it is drawn to the intake side of the blower 41.

In all of the forms of embodiment of our invention, we may use either horizontally disposed coolers, disposed in the annular space between the outer periphery of the stator core 21 and the outer cylindrical frame-shell 18, or the vertical-cooler arrangement which is shown in Figs. 1 to 10. In all forms of embodiment of our invention, or as alternatives to the previously described forms of em bodiment, we may also use a form of stator-core cooling, using axially disposed core-ventilating passages which do not discharge into the air gap 17. These alternative constructions are illustrated in Figs. 11 to 14.

in Figs. 11 to 14, our machine uses the same blower 41 as in Figs. 1 to 6, and the same rotor-ventilation. Its

cooler-arrangement is different, its stator-core ventilation is different, and its baffling, partitions, or gas-guiding means are different. The machine of Figs. ll to 14 has an inner cylindrical frame-shell 103, which is disposed inside of the outer cylindrical frame-shell 18, in spaced relation thereto. The outlet end of the blower 41 discharges into a passageway 104 which terminates in the inner cylindrical frame-shell 103 at a place which is close to, but spaced from, the end-bracket 20 of the housing.

This portion of the inner frame-shell 103, where the passageway 104 from the blower terminates, is provided, at suitable points, such as its top and bottom points, with a plurality of openings 105 (Figs. 12 and 13), which discharge the pressurized hot gases into that portion of the annular space between the two frame-shells 103 and 18.

Disposed at 45 diagonal points around the circumference of this annular space between the shells 103 and 18, are four longitudinally disposed coolers 107, which extend the entire length of the machine, from one bracket 19 to the other bracket 20. Disposed transversely across this annular space between the two shells 103 and 18, are any number, say seven, of frame-rings, 111 to 117, of which the frame-rings 112 to 117 are disposed within the length or distance which is occupied by the stator core 21, or disposed in a surrounding relation, with respect to the stator core 21; while the frame-ring 111 is disposed at an intermediate point between the hot-gas openings 105 and the nearest end of the stator core 21, or, the frame-ring 112.

The hot gas, which is discharged through the openings 105, spreads out longitudinally through the entire lengths of the spaces 106 and 106, which are bounded radially by the inner and outer frame-shells 103 and 18, and which are bounded laterally by the two top coolers 107 (for the space 106), and by the two bottom coolers 107 (for the space 106), respectively. In order to permit this longitudinal distribution of the hot gas in the spaces 106 and 106', we provide through-passageways between the frame-rings 111 to 117, at the tops and hottoms thereof, these through-passageways including openings 106", in the seven frame-rings 111 to 117, as shown in Figs. ll, 12 and 13.

As shown in Figs. 11 and 13, the hot gases leave the hot-gas spaces 106 and 106' at the top and bottom of the machine, respectively, and pass eircumferentially through the adjacent coolers 107, leaving these coolers as cold or cooled gas, which is collected in cool-gas spaces 118 and 118, which are located on the same horizontal level as the rotor member 16 of the machine, being bounded radially by the inner and outer shells 103 and 118, and being bounded circumferentially by the right-hand pair of coolers 196 (for the space 113) and by the left-hand pair of coolers (not shown, for the space 118').

The cool gas in the spaces 118 and 118' spreads out axially throughout the entire length of the machine, with in these spaces, through openings 118 in the seven frame-rings 111 to 117, these openings 113 being placed just over and under the horizontal axis, as shown in Figs. 11 and 13. From the cool-gas spaces 118 and 118, the pressurized cool gas is distributed radially inwardly, at several points along the lengths of these spaces, as will be subsequently described.

It is necessary, first, to describe the stator-core ventilating-system which is shown in Figs. 12 and 14. As shown in these figures, the stator core 21 is ventilated by means of a plurality of axially or longitudinally extending core-ventilating holes or passages 120, which extend all the way through the length of the stator core 21 from one end to the other end thereof. The cooling gas may flow uninterruptedly all the way through the entire axial length of each of these axial core-passages 120; but if the machine is very long, it may be desirable, as shown in Figs. 12 and 14, to subdivide these axial core-passages 120, in two or more places, as shown by the radial ventilating spaces 121 and 122, which are provided at spaced intermediate points in the stator core 21. These radial vent-spaces are closed at their inner, or air-gap, ends, as shown at 123; and they are open at their outer peripheries, the radial space 121 eing in communication with a peripheral annular space 121', which is just underneath the space between the two frame-rings 113 and 114, while the radial core-ventilating space 122 is in communication with a peripheral annular space 122 which is just underneath the space between the two frame-rings 115 and 116. The purposes of these spaces will soon be apparent.

Referring back, now, to the cool-gas spaces 118 and 118', as shown in Figs. 11 and 14, it will be noted that the inner frame'shell 103 is provided with certain openings which are disposed on about the same horizontal level as the rotor member 16. At the extreme end of the inner frame-shell 1033, close to the housing-bracket 20, and between this bracket 20 and the discharg-passageway 104 for the blower 41, the inner frame-shell 103 is provided with an opening or openings 124, which discharge some of the cool gas radially inwardly mto the flat end-space 124' close to the bracket 20, said gas thence flowing axially inwardly through the underblower passages 42 to the rotor-winding inlet-openings 32 at that end of the machine. At the other end of the machine, the inner frame-shell 103 is provided with one or more openings 125 (Fig. 14), which discharge cool gas into the cool-gas end-space 126, at the end of the machine which is bounded by the housing-bracket 19. This end-space 126 is in free communication with the stator-winding duct-inlets 240, the rotor-winding inletopenings 32 at that end of the machine, and the statorcore axial-passages 120 at that end of the machine. As in Fig. l, the air gap 17 is closed, or nearly closed, at this end, by the air-gap bafile 69, so that little or no air is admitted to that end of the air gap 17, from the coolgas end-space 126.

In addition to the above-described openings 124 and 125 which discharge cool gas from the spaces 118 and 118', the inner frame-shell 103 is provided with three other openings 127, 123 and 129, at about the same horizontal level as the rotor member 16, as shown in Fig. 14. The opening 127, in the inner shell 103, communicates with the previously described peripheral annular space 121, which feeds cool gas radially inwardly into the radial ventilating space 121 of the stator core, and from this point the cool gas flows, in two opposite directions, into the two adjacent portions of the axial core-passages 120. The opening 128, in the inner shell 103, is in communication with the other previously described peripheral annular space 122, but it is shut off from communication with the annular space between the two framerings 115 and 116, by means of a short radially disposed duct 128', which extends from the opening 128 into communication with a closed end of an axially disposed duct 130, which extends through the frame-rings 115, 114, 113 and 112, terminating before it reaches the frame-ring 111. This terminal end of the axial duct 130 is also closed, and is in communication with a short radial duct 129, which is in communication with the opening 129 in the inner frame-shell 103, this opening 129 discharging into the hot-gas space 24" which is in communication with the intake side of the blower 41.

In summarizing the operation of the apparatus shown in Figs. 11 to 14, it will not be noted that the cool gas in the coolgas spaces 118 and 118 is discharged in three ,different paths, at the horizontally disposed openings 124, 125 and 127. The opening 124 delivers cool gas to the left-hand end of the rotor-windings 30. The opening 127 delivers cool gas to the intermediate point 121 in the length of the axially extending stator-core ventilatingopenings 120. The opening 125 delivers cool gas to the cool-gas end-space 126 at the right-hand end of the machine, and from this space, three streams of cool gas are delivered, respectively, to the stator-winding duct-inlets 24a, the rotor-winding inlet-openings 32 at that end of the machine, and the stator-core axial-openings 120 at that end of the machine. The inner-cooling statorwinding ducts 24 discharge into the hot-gas space 24" at the left-hand end of the machine. The rotor-winding inner-cooling ducts discharge through the centrally disposed discharge-openings 34 and thence into the air gap 17, which is in turn in communication with the hot-gas space 24" at the left-hand end of the machine. The stator-core axial-openings receive cool gas at two points, as described, and discharge their heated gas into the hot-gas space 24" at the left-hand end of the machine.

The axially extending stator-core ventilating-openings 120, in Figs. 11-14, can be quite small in size, and small in number, for a combination of reasons, including the small amount of heat which remains to be extracted from the stator-core after the stator-winding heat-losses have been removed by inner-cooling, the avoidance of the introduction of hot air-gap gases into the statorcore vents, and the high hydrogen-pressure and the high blower-pressure which are needed for the inner-cooling of the stator and rotor windings. In fact, in our particular combination of inner-cooled turbine-generator, with an air gap which is devoted exclusively to the collection and conduction of hot gases, we believe that the volume of the stator-core may be appreciably reduced, by using axial core-vents instead of the usual radial vents.

In all forms of our invention, it is to be noted that there is no commingling of hot and cold gases in the air gap 17, which is reserved, in all the forms of embodiment of our invention, for exclusive use as a hotgas receiving-chamber.

It is to be understood that our invention is not limited to the precise forms of embodiment which have been chosen for the illustration of the principles of the in vention; as many changes can be made, in the way of adding refinements, omitting unnecessary features, changes in shape and arrangement, and the substitution of equivalents, without departing from the essential spirit of the invention.

We claim as our invention:

1. A dynamoelectric machine having a stator member and a rotor member separated by an air gap; (a) said stator member having a cylindrical stator core having a plurality of axially extending winding-receiving statorslots, and a stator winding having coil-sides lying within the winding-receiving stator-slots; (b) said rotor memher having a cylindrical rotor core having a plurality of axially extending winding-receiving rotor-slots, and an inner-cooled rotor winding having coil-sides lying within the Winding-receiving rotor-slots, said rotor winding having rotor-winding cooling-ducts in good thermal relation to the rotor-conductors for substantially directly cooling sa1d rotor-conductors, said rotor-winding cooling-ducts having inlet-openings at the respective ends of the rotor winding and having outlet-openings at a plurality of intermediate discharge-points within the windin receiving rotor-slots, said rotor windings being insulated for a voltage which is considerably lower than said stator windlugs, and said rotor core having a plurality of radially extending rotor-ducts extending between the respective outlet-openings of the rotor-Winding cooling-ducts and the air gap; (0) said stator member further including a substantially gas-tight machine-enclosing housing having a gaseous filling, said housing (c) having a core-surrounding housing-portion, surrounding the stator core, in combination with a means for providing a through duct-means extending axially from one end of the machine to the other; (0.) said air gap being sufficiently large to act as a hot-gas collecting-chamber and as an axial duct for a substantial portion of the ventilating-gas of the machine; (e) a blower, carried by the rotor member at at least one end of the rotor core, and directed so as to evacuate hot gas from that end of the air gap, said blower including a supporting-means which provides an axially extending under-blower passage near the rotor-shaft, the inner end of said under-blower passage being in communication with the rotor-winding inlet-openings of item (in) at that end of the machine; (f) heat-exchanging means disposed within said housing (0) and (g) a recirculating cooling-system comprising a gas-circulation guidingneans, for causing a plurality of streams of rotor-winding ventilating-gas to flow axially inwardly into all of the rotor-winding inlet-openings of item (b) from both ends of the rotor-member; said gas-circulation guiding-means including: a means for guiding the hot gas which is discharged from said blower (e) first through said heatexchanging means (1) to cool said gas; a gas-communication means, at one end of the machine, for placing at least some of the cooled gas in communication with that end of the through duct-means of item (c); and a gascommunication means, at each end of the machine, for placing its end of the through duct-means in communication with the rotor-winding inlet-openings of item (b) at its end of the machine.

2. The invention as defined in claim 1, characterized by the gaseous filling of item being a gas having a molecular weight lower than nitrogen, at a gas-pressure which is adapted, at times, to be at least as high as 30 pounds per square inch, gauge.

3. The invention as defined in claim 1, characterized as follows: (aa) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors; and (h) a recirculating stator-winding cooling-system comprising: a means for recirculating a stator-winding cooling-fluid in said stator-winding cooling-ducts; and a means for cooling said stator-winding cooling-fluid.

4. The invention as defined in claim 1, characterized as follows: (an) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors, said stator-winding cooling-ducts having outlet-openings at one end of the machine and inlet-openings at the other end of the machine; and (gg) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-winding ventilating-gas to flow through the stator-winding cooling-ducts of item (an), said gas-circulation guiding-means also including: a means for guiding some of the cooled gas from the heat-exchanging means (f) to the inlet-openings of item (zza); and a means for returning hot gas from the outlet-openings of item (ml) to the suction side of the blower (e).

5. The invention as defined in claim 1, characterized as follows: (e') the blower (e) being present at only one end of the r0tor-core; and (g') the gas-circulation guiding means (g) further including a means for substantially closing the air gap at said other end of the machine.

6. The invention as defined in claim 5, characterized as follows: (aa) the stator winding being an inner-cooled winding having stator-Winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors; and (h) a recirculating stator-winding cooling-system comprising: a means for recirculating a stator-winding cooling-fluid in said stator-winding cooling-ducts; and a means for cooling said stator-winding cooling-fluid.

7. The invention as defined in claim 5, characterized as follows: (ml) the stator winding being an inner-cooled winding having stator-Winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors, said stator- Winding cooling-ducts having outlet-openings at the blower-end of the machine and inlet-openings at the other end of the machine; and (gg) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-winding ventilating-gas to flow through the stator-winding cooling-ducts of item (an); said gas-circulation guiding-means also including: a means for guiding some of said cooled gas to the inletopenings of item (an) at the said other end of the machine; and a means for returning hot gas from the outlet-openings of item (aa) to the suction side of the blower (e).

8. The invention as defined in claim 1, characterized as follows: (a') the stator member having a plurality of radially extending core-ventilating stator-ducts having their outer ends extending to the outer periphery of the stator core; (0) the housing (0) also including a means for providing an axially extending peripherally disposed core-ventilating passage in a space between the outer periphery of the stator core and the core-surrounding housing-portion of item (0), said passage being in communication with the outer peripheral ends of substantially all of the radially extending core-ventilating statorducts (a); and (g') the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-core ventilating-gas to How radially inwardly through all of the radially extending stator-ducts of item (a), said gas-circulation guiding-means also including: a means for guiding some of the cooled gas from said heat-exchanging means (f) to said axially extending core-ventilating passage of item (0); and a means for returning hot gas from the inner ends of the radially extending core-ventilating stator-ducts of item (a) to the suction side of the blower (e).

9. The invention as defined in claim 8, characterized as follows: (aa) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors; and (h) a recirculating stator-winding cooling-system comprising: a means for recirculating a stator-winding cooling-fluid in said stator-winding cooling-ducts; and a means for cooling said stator-winding cooling-fluid.

10. The invention as defined in claim 8, characterized as follows: (aa) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors, said stator-winding cooling-ducts having outlet-openings at one end of the machine and inlet-openings at the other end of the machine; and (gg) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-winding ventilating-gas to ilow through the stator-winding cooling-ducts of item ((111), said gas-circulation guiding-means also including: a means for guiding some of the cooled gas from the heat-exchanging means (1) to the inlet-openings of item (an); and a means for returning hot gas from the outlet-openings of item (an) of the suction side of the blower (e).

11. The invention as defined in claim 1, characterized as follows: (a') the stator member having a plurality of radially extending core-ventilating statorducts having their outer ends extending to the outer periphery of the stator core; (0) the housing (0) also including a means for providing an axially extending peripherally disposed core-ventilating passage in a space between the outer periphery of the stator core and the core-surrounding housing-portion of item (0), said passage being in communication with the outer peripheral ends of substantially all of the radially extending core-ventilating statorducts (a); axially from one end of the machine to the other, in a space between the outer periphery of the stator core and said core-surrounding portion of the housing; (e) the blower (2) being present at only one end of the rotor-core; (g) the gas-circulation guidingmeans (g) being a means which also causes a plurality of streams of stator-core ventilating-gas to How radially inwardly through all of the radially-extending stator-ducts of item (a), said gas-circulation guiding-means also including: a means for substantially closing the air gap at said other end of the machine; a means for guiding some of the cooled gas from said heat-exchanging means (f) to said axially extending core-ventilating passage of item (c'); and a means for returning hot gas from the inner ends of the radially extending core-ventilating stator-ducts of item (a) to the suction side of the blower (e):

12. The invention as defined in claim 11, characterized as follows: (an) the stator winding being an innercooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors; and (h) a recirculating stator-winding cooling-system comprising: a means for recirculating a stator-winding cooling-fluid in said stator-winding cooling-ducts; and a means for cooling said stator-winding cooling-fluid.

13. The invention as defined in claim 11, characterized as follows: (an) the stator winding being an innercooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors, said stator-winding cooling-ducts having outlet-openings at the blower-end of the machine and inlet-openings at the other end of the machine; and (gg) the gas-circulation guiding-means (g) being a means which alsocauses a plurality of streams of stator-winding ventilating-gas to flow through the stator-winding cooling-ducts of item (fill), said gas-circulation guiding means also including: a means for guiding some of said cooled gas to the inletopenings of item (aa) at the said other end of the machine; and a means for returning hot gas from the outlet-openings of item (on) to the suction side of the blower (e).

14. The invention as defined in claim 1, characterized as follows: (a) the stator member having a plurality of radially extending core-ventilating stator-ducts extending between the outer periphery of the stator core and the air gap; the housing (0) also including a means for providing an axially extending peripherally disposed core-ventilating passage in a space between the outer periphery of the stator core and the core-surrounding housing-portion of item (c), said passage being in communication with the outer peripheral ends of substantially all of the radially extending core-ventilating stator-ducts (a); and (g) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-core ventilating-gas to flow radially inwardly through all of the radially extending stator-ducts of item (a), said gas-circulation guiding-means also including: a means for guiding some of the cooled gas from said heat exchanging means (f) to said axially extending core-ventilating passage of item (c).

15. The invention as defined in claim 14, characterized as follows: (aa) the stator winding being an inner-cooled Winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors; and (h) a recirculating stator-winding cooling-system comprising: a means for recirculating a stator-winding cooling-fluid in said stator-winding cooling-ducts; and a means for cooling said stator-winding cooling-fluid.

16. The invention as defined in claim 14, characterized as follows: (an) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors, said stator-winding cooling-ducts having outlet-opening at one end of the machine and inlet-openings at the other end of the machine; and (gg) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of statorwinding ventilating-gas to flow through the stator-winding cooling-ducts of item (an), said gas-circulation guiding-means also including: a means for guiding some of the cooled gas from the heat-exchanging means (f) to the inlet-openings of item (aa); and a means for returning hot gas from the outlet-openings of item (aa) to the suction side of the blower (e).

17. The invention as defined in claim 1, characterized as follows: (a') the stator member having a plurality of radially extending core-ventilating stator-ducts extending between the outer periphery of the stator core and the air gap; (0') the housing (0) also including a means for providing an axially extending peripherally disposed coreventilating passage in a space between the outer periphery of the stator core and the core-surrounding housing-portion of item (0), said passage being in communication with the outer peripheral ends of substantially all of the radially extending core-ventilating stator-ducts (a'); (e) the blower (e) being present at only one end of the rotor-core; (g) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-core ventilating-gas to flow radially inwardly through all of the radially extending stator-ducts of item (a), said gas-circulation guiding-means also including: a means for substantially closing the air gap at said other end of the machine; and a means for guiding some of the cooled gas from said heat-exchanging means (7) to said axially extending core-ventilating passage of item (0').

18. The invention as defined in claim 17, characterized as follows: (aa) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors; and (h) a recirculating stator-winding cooling-system comprising: a means for recirculating a stator-winding cooling-fluid in said stator-winding cooling-ducts; and a means for cooling said stator-winding cooling-fluid.

19. The invention as defined in claim 17, characterized as follows: (aa) the stator winding being an inner-cooled winding having stator-winding cooling-ducts in good thermal relation to the stator-conductors for substantially directly cooling said stator-conductors, said stator-winding cooling-ducts having outlet-openings at the blower-end of the machine and inlet-openings at the other end of the machine; and (gg) the gas-circulation guiding-means (g) being a means which also causes a plurality of streams of stator-winding ventilating-gas to flow through the statorwinding cooling-ducts of item (aa), said gas-circulation guiding-means also including: a means for guiding some of said cooled gas to the inlet-openings of item (aa) at the said other end of the machine; and a means for returning hot gas from the outlet-openings of item (aa) to the suction side of the blower (6).

References Cited in the file of this patent UNITED STATES PATENTS 2,185,728 Fechheimer Jan. 2, 1940 2,573,670 Moses Oct. 30, 1951 2,663,808 Rosenberg Dec. 22, 1953 FOREIGN PATENTS 518,207 Great Britain Feb. 20, 1940 

